Caesar Shift Decrypt

@never_cache
def caesar_decrypt(request):
    
    def caesar_shift(crypt_text):
        table = string.maketrans(
                string.ascii_lowercase,
                string.ascii_lowercase[13:]+string.ascii_lowercase[:13])
        return string.translate(crypt_text.encode(errors="ignore").lower(), table)
    
    if request.method == 'POST':
        cipher_text = request.POST.get('cipher_text')
        if cipher_text:
            template_dict['clear_text'] = caesar_shift(cipher_text)
    
    return render_to_response('caesar_decrypt.html', template_dict, context_instance=RequestContext(request))